1. Field of Invention
This invention generally relates to miniature cameras and, more particularly, to shutters for miniature cameras.
2. Related Art
Miniature cameras are currently available with many electronic devices, such as cellular telephones, laptop computers, personal digital assistants (PDAs), and the like. Miniature cameras are also available as stand-alone devices for applications such as security and surveillance.
The market for miniature cameras is rapidly expanding. For example, camera-equipped cell phones were unheard of just a few years ago; now, they are a significant portion of the cell phone market. However, available miniature cameras may not be optimal for some applications.
Camera shutters were developed to control the transmission of light through the camera's optical system to a film material. In a film (non-digital) camera, the shutter is positioned in front of the camera optics prior to film exposure. To begin the picture taking process, the user presses a button. In response, the shutter moves to a position that allows light to reach the camera optics, and film exposure begins. After the desired exposure time has elapsed, the shutter moves back to the initial position in front of the camera optics. Film advance mechanisms move the exposed film away from the exposure position, while un-exposed film is moved to the exposure position to be exposed at a later time.
Unlike film cameras, digital cameras need not include a mechanical shutter. Instead, shuttering may be performed electronically. However, some digital camera systems use a mechanical shutter in addition to electronic shuttering. FIG. 1 shows an example of a mechanical shutter system 100, according to the prior art.
Shutter system 100 includes a mechanical shutter 130 with a pivot pin 135 and an actuator 140. System 100 is included as part of a digital camera 110, which has a light aperture 120 configured to receive light to be processed to generate image information for an exposure. Note that the term “exposure” in the context of digital photography refers to the time during which light is received for a particular digital image, rather than a time during which film is exposed.
Digital camera 110 includes a controller (not shown) and a digital imaging system (not shown), such as a CMOS (complementary metal-oxide semiconductor) system or a CCD (charge coupled device) imaging system. Received light corresponding to a matrix of image pixels is processed to generate a digital image.
In contrast to the film camera described above, shutter 130 may initially be positioned away from aperture 120. The user may push a button 125 to begin the exposure. In response, the controller may zero the pixels of the digital imaging system to begin digital image data acquisition. At the end of the exposure time, shutter 130 may be moved in front of aperture 120 to indicate the end of the image. In order to move shutter 130, a force may be applied using actuator 140 to rotate shutter 130 about the pivot point created by pivot pin 135. After a short time, the force may be removed, so that shutter 130 moves back to its initial position away from aperture 120.